In boating and more especially in recreational boating, accessories are more and more numerous and sophisticated, whereby onboard electronics, a microwave-equipped kitchen, television, pressurized water and other deck gear are powered by electricity.
Actually for most recreational craft, comfort is an essential criterion of choice.
This invention relates to limited capacity units without independent generating sets and with an “inboard” engine.
Motorized marine craft are distinguished from sailing craft and electrically-propelled craft.
In both cases, the engine is equipped with at least one alternator that allows the charging of the engine battery set. This engine battery set is used for engine functions and especially for starting.
Conversely, it is rarely large enough for services and comfort.
Moreover, in the case of a single set, a first problem arises when the engine battery set has been heavily loaded. Actually, when the engine is started, the alternator or alternators are subjected to a very strong demand for current for which they are not designed. This generally causes these charging means to be shut down, thus the propulsion is shut down.
Since the engine is critical for a motor craft and at least is a safety element for sailing craft, it would seem necessary to be able to divide the battery set into an engine battery set and a service battery set.
The former is generally composed of one or two high amperage batteries connected to an alternator, one for each engine if there are several engines.
The latter is generally composed of a larger number of batteries, optionally of different types and voltages, in order to have a high electric power storage capacity. It is then a good idea to be able to recharge these batteries.
In marine propulsion systems, for a propulsion system, the following are systematically found: an engine, a transmission, and a propeller or a turbine.
Transmissions are of different types and generally consist of a reducing gear, optionally a reversing gear, with a propeller drive by a direct shaft assembly or by a Sail-drive or Z-drive type.
Thus, the engine has an engine shaft output that is equipped with an inertial flywheel, this system being located in a standardized shroud to accommodate the different transmission types according to the different suppliers.
The coupling between the engine shaft that is equipped with its inertial flywheel and the transmission shaft is of the elastic type known under the name of “flector”.
This makes it possible to absorb expansions, alignment tolerances, and vibrations.
To be able to meet the needs of electric power generation, one approach consists in interposing a large-sized generator between the engine and the transmission.
This has the advantage of not dictating design modifications of the marine craft, at the very most shifting the engine mount position on the order of 15 to 30 cm to provide an order of magnitude.
It is noted that this modification is minor on new constructions and can be easily performed on existing marine craft.
In terms of diameter, there is no problem of overcrowding in this area.
The prior art thus proposes in Patent Application WO 2005/032935 or EP 1 669 287 a generator that is interposed between the engine and the transmission.
Very numerous variants call for specific housings connected to the engine block, even specific flywheels; this requires major modifications on existing systems and on new engine systems that are modified according to whether they do or do not accommodate a generator.
Regardless of the arrangement adopted, there is a problem of operation.
Actually, the flywheel is carried by the drive shaft, therefore guided by a bearing mounted on the engine block. The rotors are connected to this flywheel and constitute a significant mass, 10 to 15 kg to give an order of magnitude, at the start. The stators are integral with the generator housing, this housing being connected to the engine output shroud, and the stators are located to the right of the rotors with an air gap of several tens of millimeters.
On the other hand, the elastic coupling makes it possible to drive the driven shaft that is itself carried by a bearing mounted on the reducing gear block.
It is noted that the rotors can undergo rotation with slight barrel deformation due to bending between the two bearings.
This barrel rotation is poorly compatible with the rotor/stator air gap of several tens of millimeters.
One major problem is therefore intermediate guidance.